A Polymer Electrolyte Membrane (PEM) fuel cell typically comprises electrodes, an electrolyte, a catalyst, and gas diffusion layers. A mixture of catalyst, carbon, and electrode is coated onto the solid electrolyte and carbon is hot pressed on either side to protect the inside of the cell and also act as electrodes. The cell reactions occur at the triple phase boundary (TPB) where the electrolyte, catalyst, and reactants mix.
The membrane conducts hydrogen ions but not electrons and it must also not allow gas from one side of the cell to pass to the other. Splitting of the hydrogen molecule is relatively easy by using a platinum catalyst.
Oxygen reduction reaction (ORR) catalysts play an essential role in large-scale implementation of PEM fuel cells and those on the market tend to use noble metals, such as platinum, iridium and ruthenium, due to their low overpotential and high current density. However, such catalysts suffer from problems like high cost, scarcity, aggregation in alkaline electrolytes, susceptibility to methanol, and carbon monoxide (CO) poisoning
Transition metal-based and heteroatom-doped carbon materials are regarded as promising replacements for commercial catalysts in oxygen reduction reactions for PEM fuel cells and metal-air batteries.
However, in most cases researchers mainly focus on introducing foreign species on the surface or in the void space of carbon nanostructures, potentially leading to loose attachment and aggregation of the dopants, thus the synergetic effect between the dopant and carbon structure is compromised.
An aim of the invention therefore is to provide a material for an ORR catalyst which overcomes the above issues.